A significant amount of research and development has been undertaken in recent years towards generation of energy from natural sources, such as sun and wind. Attempts to reduce reliance on oil and coal, such as from foreign sources, have become an important issue. Energy experts fear that some of these resources, including oil, gas and coal, may someday become exhausted.
Solar energy is known as a type of various clean energy sources that can be converted to produce electricity. However, the output of a solar power generating system relies to a great extent on weather conditions. For instance, many solar panels are designed to convert solar energy only during sunny daylight hours. They do not produce significant amounts of energy on cloudy days or during night hours.
While solar thermal power may be the most widely known natural source, there exists also the potential for harnessing significant amounts of energy from wind. Wind farms, for example, have been built in many areas where the wind naturally blows. To use wind energy for generation of electricity is a clean, renewable, and ecologically-friendly alternative to traditional fossil-based energy supplies.
One drawback of using wind as an energy source, however, is that the wind does not always blow, and even if it does, it does not always blow at the same speed, i.e., it is not always reliable. The wind also does not blow consistently throughout different times of the day, week, month and seasons of the year, i.e., it is not always predictable. Thus, due to the seasonal and daily variations in wind speed and power, the output of wind electrical generators often fluctuates, and is not reliable.
Accordingly, a major impediment to large-scale penetration of wind and solar energy is the variable and intermittent nature of solar and wind renewable resources. Intermittency leads to an unstable power output, causing significant challenges for distribution through the electric grid. The latter challenge also manifests itself into power-curtailing issues, which are becoming more and more apparent these days in the wind industry. Since wind energy in certain areas is mostly available during the night when the demand is low, it is required that the power from wind farms be curtailed to prevent overloading the grid.
Systems and methods for providing an integrated and complementary energy generating system capable of converting wind and solar energy for use with electrical generators are known in the art. During the daytime, such hybrid systems can concurrently derive energy from both wind and solar energy sources. During the nighttime, the systems can continuously harvest wind energy, regardless of weather conditions. As the peak of wind flow and sunlight tends to occur at different times of the day and year (for instance, winds are stronger in the winter with less sunlight and also stronger during nighttime), these two energy sources can complement each other.
For example, U.S. Pat. No. 4,229,941 to Hope describes a unitary system for generating electrical energy from solar and wind energy sources. The system includes a solar collector that collects solar rays, and these rays are focused by a parabolic mirror before being conducted through a fresnel tube to a container which minimizes thermal exchange with the exterior environment. The thermal energy of the rays within the container is converted to mechanical energy by a boiler and a steam-operated turbine. A wind collector converts air currents to mechanical energy which is selectively mechanically coupled to the mechanical energy derived from the solar collector prior to being converted to electrical energy.
U.S. Pat. No. 6,661,113 describes a power generating system that includes a base assembly that has a lower portion and an upper portion. The lower portion is for supporting the upper portion of the base assembly. A solar assembly is coupled to the upper portion of the base assembly. A power storage assembly is operationally coupled to the solar assembly. The power storage assembly is for storing electricity from the solar assembly. The power storage assembly is positioned in the lower portion of the base assembly such that the lower portion of the base assembly is for protecting the-power storage assembly from adverse weather. A turbine assembly is coupled to the upper portion of the base assembly. The turbine assembly is for producing electricity from wind. The turbine assembly is operationally coupled to the power storage assembly such that the power storage assembly is for storing electricity produced from the turbine assembly.
U.S. Pat. No. 7,172,386 to Sosonkina et al. describes a wind and solar power plant, producing electrical energy. The system comprises rotor trains, mounted on decks of a garage-like building, each rotor train having a plurality of rotors positioned between a shroud and a wind tunnel. The wind is accelerated in a low middle part of the wind tunnel while it flows from a high entrance towards a higher and wider exit. The blades of the rotors protrude into the middle part of the wind tunnel causing fast rotation of the rotors around horizontal axes. A super-diffuser, a booster and a wind tunnel increase the power of the wind and rotors hundreds of times. Each rotor train comprises up to six rotors connected with twelve electrical generators. Electrical energy can be also produced by solar panels, mounted on the balconies and on the roof of a building.
U.S. Pat. No. 7,964,981 to Tsao describes an integrated hybrid energy generating system capable of converting wind and solar energy for use with an electrical generator. The system includes a wind powered subsystem including: a rotor for receiving wind to generate mechanical energy; and a first shaft for providing a permanent mechanical coupling between the rotor and the electrical generator for transferring the generated mechanical energy to the electrical generator. The system also includes a solar powered subsystem including: a solar collector for receiving solar energy to generate thermal energy; a thermo-mechanical engine coupled to the solar collector for converting the generated thermal energy into mechanical energy; and a second shaft mechanically coupled to the thermo-mechanical engine; and an interconnection subsystem for selecting between coupling the second shaft to the first shaft for combining the mechanical energy generated by the wind and solar powered subsystems to be transferred to the electrical generator, and decoupling the second shaft from the first shaft. During the daytime, the system concurrently derives energy from both wind and solar energy sources. During the nighttime, it continuously harvests wind energy, regardless of weather conditions.